Building on the design by Russian amateur telescope maker and astronomer Pavel Bahtinov, the Farpoint Tri-Bahtinov Focus and Collimation Mask can be used to quickly and easily confirm your OTA's collimation and then focus your telescope for all types of astrophotography with DSLRs or imaging systems. The "Tri" in the name refers to the advanced design of the mask—it is essentially three masks in one unit, rotated over 120-degrees, that gives you three lines and three crosses to check the collimation along three axes at the same time.
Made of durable ABS plastic, the mask is designed specifically for Celestron's 11" Rowe-Ackermann Schmidt Astrograph (RASA), and simply fits into the dew shield or objective retaining ring. It takes the guesswork out of focusing on astronomical objects and ensures tack-sharp views of stars, planets, and just about any other celestial subject you want to photograph or image.